Wavelength blockers are well known and commonly used in telecommunications applications for routing signals. U.S. Pat. No. 6,504,970 in the name of Doerr assigned to Lucent Technologies Inc. (Murray Hill, N.J.) incorporated herein by reference discloses a planar lightwave circuit having shutter array disposed between an arrayed waveguide grating (AWG) multiplexer and a demultiplexer for selectively passing or blocking N wavelength signals. In Doerr's device, a wavelength blocker selectively blocks one or more wavelengths or channels from reaching a destination, while allowing other wavelengths or channels to pass to the destination The wavelength blocker device has a plurality of input ports and a plurality of output ports. Doer describes wavelength blockers as devices for accepting an incoming signal of multiple wavelength channels and for independently passing or blocking particular wavelength channels. Wavelength blockers can be used as components in a larger optical communication system, for example, to route a given optical signal along a desired path between a source and destination. Optical cross-connect switches and wavelength add-drop multiplexers, for example, could be implemented using wavelength blockers.
The instant invention, utilizes the wavelength blocking function and obviates the requirement for a costly array of detectors to form an optical performance monitor with an integration of a channel selectable filter.
If integratable components were available at little or no cost, it would likely be simpler when designing an optical performance monitor to design a system that had an integrated demultiplexer to separate an incoming multiplexed signal having n channels having n distinct center wavelengths to n spatially distinct locations, and to place n detectors at those locations to detect a characteristic of each of the n signals, for example signal power. By parallel processing in this manner, the detected power levels of the n channels could be quickly and simply compared.
Unfortunately, this configuration blocked the possibility of signal passthrough for a further signal analysis. Furthermore, utilizing an array of n detectors may require calibration to ensure that responses are matched and the n detectors require alignment and coupling to n waveguides which adds to the cost and complexity of an optical performance monitor.
It is an object of this invention, to provide an optical performance monitor or power monitor that requires fewer detectors than channels to be analyzed and simultaneously an optical channel filter for further signal process.
It is a further object of this invention to provide an optical performance monitor that is substantially integrated within a single chip and which requires few detectors, preferably one, time-shared with between the signals to be analyzed.